1. Field
Embodiments of the disclosure relate generally to the field of aerodynamic flap extension mechanisms for aircraft and more particularly to a compact operating linkage with substantially linear motion in a small range about the retracted position but providing large Fowler extension and rapid droop.
2. Background
For modern commercial jet aircraft, flaps which work with drooping spoilers for take-off and landing positions and also provide a small range of cruise positions are becoming necessary for improved efficiency. The flap mechanism required for this very desirable capability, when combined with a need for large Fowler motion, can be deep and wide and require a large aerodynamic fairing which causes excessive cruise drag.
The combination of drooping spoiler landing positions and multiple cruise positions known as “trailing edge variable camber” (TEVC) has been recently introduced in commercial aircraft. Current designs have relatively small trailing edge flaps with relatively small Fowler motion, i.e. aftward motion that increases the wing chord length or plan form. An example of a current design is a simple hinged flap where the flap pivots about a spanwise hinge axis which is stationary with respect to the wing fixed primary structure. With the need for larger flaps and increased Fowler motion, the flap hinge axis must be offset a greater distance below the wing. This results in a larger fairing to accommodate a deeper hinge and larger flap support structure. The larger fairing increases airplane aerodynamic drag. An example of such simple hinged flap is described in U.S. Pat. No. 7,891,611.
It is therefore desirable to provide a flap system with large Fowler motion and good take-off and landing flap positions compatible with drooping spoilers, and also a range of aerodynamically sealable cruise positions, all in a compact package for greatly improved cruise drag.